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This study investigated the growth, survival and fatty acid composition of sea urchin Paracentrotus lividus larvae fed four microalgal diets: Cricosphaera elongata, Pleurochrysis carterae, Tetraselmis suecica and Dunaliella tertiolecta (control). Larvae were successfully raised to competence for metamorphosis when fed C. elongata, P. carterae and D. tertiolecta diets but significant differences were found in survival rate and development. Larvae fed C. elongata showed 3 times higher survival and 20 % faster development than larvae fed the other two microalgae diets that supported development. In contrast, T. suecica failed to fully support development and larvae stalled at the four arms stage for more than 30 days. The urchin larvae could accumulate long-chain polyunsaturated fatty acids (LC-PUFA) such as docosahexaenoate (DHA; 22:6n-3), eicosapentaenoate (EPA; 20:5n-3) and arachidonate (ARA; 20:4n-6), either by assimilation and retention of dietary fatty acids, and/or synthesis from α-linolenic acid 18:3n-3 and linoleic acid 18:2n-6. Moreover, an accumulation of n-3 LC-PUFA and higher EPA/DHA and EPA/ARA ratios appeared to be associated with improved larval performance. The results indicate that live microalgae species, with appropriate fatty acid profiles are able to improve P. lividus larval performance, ultimately increasing hatchery profitability.

Sea urchins are broadly recognised as a delicacy and their quality as food for humans is highly influenced by their diet. Lipids in general and the long-chain polyunsaturated fatty acids (LC-PUFA) in particular, are essential nutrients that determine not only the nutritional value of sea urchins but also guarantee normal growth and reproduction in captivity. The contribution of endogenous production (biosynthesis) of LC-PUFA in sea urchins remained unknown. Using Paracentrotus lividus as our model species, we aimed to characterise both molecularly and functionally the repertoire of fatty acyl desaturases (Fads), key enzymes in the biosynthesis of LC-PUFA, in sea urchins. Three Fads, namely FadsA, FadsC1 and FadsC2, were characterised. The phylogenetic analyses suggested that the repertoire of Fads within the Echinodermata phylum varies among classes. On one hand, orthologues of the P. lividus FadsA were found in other echinoderm classes including starfishes, brittle stars and sea cucumbers, thus suggesting that this desaturase is virtually present in all echinoderms. Contrarily, the FadsC appears to be sea urchin-specific desaturase. Finally, a further desaturase termed as FadsB exists in starfishes, brittle stars and sea cucumbers, but appears to be missing in sea urchins. The functional characterisation of the P. lividus Fads confirmed that the FadsA was a Δ5 desaturase with activity towards saturated and polyunsaturated fatty acids (FA). Moreover, our experiments confirmed that FadsA plays a role in the biosynthesis of non-methylene interrupted FA, a group of compounds typically found in marine invertebrates. On the other hand, both FadsC desaturases from P. lividus showed Δ8 activity. The present results demonstrate that P. lividus possesses desaturases that account for all the desaturation reactions required to biosynthesis the physiological essential eicosapentaenoic and arachidonic acids through the so-called “Δ8 pathway”.

The development of diagnostic markers has been a long-standing interest of population geneticists as it allows clarification of taxonomic uncertainties. Historically, there has been much debate on the taxonomic status of species belonging to the Mytilus species complex (M. edulis, M. galloprovincialis and M. trossulus), and whether they are discrete species. We analysed reference pure specimens of M. edulis, M. galloprovincialis and M. trossulus, using Restriction site associated DNA (RAD) sequencing and identified over 6,000 SNP markers separating the three species unambiguously. We developed a panel of diagnostic SNP markers for the genotyping of Mytilus species complex as well as the identification of hybrids and interspecies introgression events in Mytilus species. We validated a panel of twelve diagnostic SNP markers which can be used for species genotyping. Being able to accurately identify species and hybrids within the Mytilus species complex is important for the selective mussel stock management, the exclusion of invasive species, basic physiology and bio-diversity studies.

Fatty acid profiles during gametogenesis in sea urchin (Paracentrotus lividus): Effects of dietary inputs on gonad, egg and embryo profiles, Comparative Biochemistry and Physiology, Part A (2012), doi: 10.1016/j.cbpa.2012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractThe effects of dietary fatty acids on the composition of Paracentrotus lividus gonads were investigated to determine whether dietary inputs affect their relative abundance during gametogenesis. Egg and embryo FA compositions were compared with that of mature gonads to understand how maternal FA are transferred to the offspring. Urchins were fed an experimental pellet diet in comparison to brown kelp (Laminaria digitata). FA profiles of diets, gonads, eggs and embryos revealed the presence in gonads of FA that were absent in the diets and/or higher contents of some long-chain polyunsaturated fatty acids (LC-PUFA). Moreover, some unusual FA, such as non-methylene interrupted (NMI), were found in gonads, eggs and embryos, but not in the diets, suggesting that P. lividus may be capable of synthesizing these FA and accumulating them in the eggs. A description of gonad FA profiles during gametogenesis is reported for the first time and data suggest that eicosapentaenoic and docosahexaenoic acids are accumulated during gametogenesis, while arachidonic acid is highly regulated and is the only LC-PUFA clearly accumulated into the eggs along with NMI. Further studies are required to determine if maternal provisioning of FA has the potential to influence sea urchin production outputs and increase hatchery profitability.